North Korea says it just tested a hydrogen bomb, its most powerful nuclear weapon yet

North Korea announced it detonated a thermonuclear device Sunday in its sixth and most powerful nuclear test to date, a big step toward its goal of developing nuclear weapons capable of striking anywhere in the U.S. The North called it a "perfect success" while its neighbors condemned the blast immediately. Though the precise strength of the blast has yet to be determined, South Korea’s weather agency said the artificial earthquake it caused was five to six times stronger than tremors generated by its previous tests. It reportedly shook buildings in China and in Russia.